RADAR detectors warn drivers of the use of police RADAR, and the potential for traffic citations if the driver exceeds the speed limit. The FCC has allocated several regions of the electromagnetic spectrum for police RADAR use. The bands used by police RADAR are generally known as the X, K and Ka bands. Each relates to a different part of the spectrum. The X and K bands are relatively narrow frequency ranges, whereas the Ka band is a relatively wide range of frequencies. By the early 1990's, police RADAR evolved to the point that it could operate almost anywhere in the 2,600 megahertz wide Ka band. During that time RADAR detectors kept pace with models that included descriptive names like “Ultra Wide” and “Super Wide.” More recently, police have begun to use laser (optical) systems for detecting speed. This technology was termed LIDAR for “light Detection and Ranging.”
Unlike LIDAR, police RADAR directly determines a vehicle's speed by measuring the doppler shift in its returned frequency (such as the increasing or decreasing pitch of an approaching or receding train or emergency vehicle). Instant-on or pulsed low-powered RADAR has been in use for many years. For some time to come, this will likely constitute the greatest occurrence in any area that has not already switched exclusively to police laser speed enforcement. Most contemporary police RADAR guns operate on the wide Ka-band RADAR. K-band RADAR still is extremely common, given it historical advantage to Ka RADAR. X-band is also still widely deployed in some areas, however, newer digital (DSP) police RADAR guns are steadily coming on-line which operate primarily on the newer Ka band.
RADAR detectors typically comprise a microwave receiver and detection circuitry that is typically realized with a microprocessor or digital signal processor (“DSP”). Microwave receivers are generally capable of detecting microwave components in the X, K, and very broad Ka band. In various solutions, either a microprocessor or DSP is used to make decisions about the signal communicated from the microwave receiver. Systems including a digital signal processor have been shown to provide superior performance over solutions based on conventional microprocessors due to the DSP's ability to rapidly find and distinguish signals that are buried in noise.
The DSP or microprocessor in a contemporary RADAR detector is programmable. Accordingly, they can be instructed to manage all of the user interface features such as input switches, lights, sounds, as well as generate control and timing signals for the microwave receiver and/or a laser detector. Early in the evolution of the RADAR detector, consumers sought products that offered a better way to manage the audible volume and duration of warning signals. Good examples of these solutions are found in U.S. Pat. Nos. 4,631,542, 5,164,729, 5,250,951, and 5,300,932, each of which is hereby incorporated by reference, which provide methods for conditioning the response generate by the radar detector.
However, these and other radar detectors still typically have an analog basic detection method, usually involving an FM demodulator. The resultant analog signal is then processed by a digital microcontroller. A problem with using an analog detection technique is that the analog detection has a slow response time. Since a detector must scan a wide range of frequencies in search of radar signals, scan speed is an important aspect of the detector. Unfortunately, analog detection methods involving FM demodulators only allow detectors to look at a narrow frequency bands at specific times, in order to achieve good sensitivity to RADAR signals over any noise. The narrow bands may assist in the problem that many detectors have been faced with; namely, their inability to detect short pulsed radar signals, which may occur at any frequency in the X, K or Ka bands. In other words, it has become more difficult to achieve a good compromise between response time and sensitivity using narrow-band analog detection methods. This problem has become even more apparent lately as more RADAR guns have started to implement short pulsed sources, known as POP-mode RADAR.
The idea behind POP-mode RADAR is simple in principle. If a RADAR gun transmits a sole pulsed RADAR wave, and that transmission only lasts 67 ms, conventional RADAR detectors won't likely spot the RADAR beam of such short duration as they are busy sweeping (scanning) multiple bands within the X, K, and Ka bands. While the 67 ms version of POP-mode RADAR has essentially been mitigated by most of the major contemporary detector manufacturers, even quicker versions of POP-mode RADAR have been introduced having pulse durations of 16 ms. Even the top of the line models of the contemporary detectors struggle with identifying this shorter duration POP-mode and the detector only alerts to the pulsed waves about one out of every 10 bursts.
Therefore there is a need in the art for a RADAR detector that is able to sweep multiple bands with sufficient speed and sensitivity to be able to detect POP-mode and other short duration bursts.